Well, one possible storyline could be about their relationship growth before they got married. Maybe exploring how they first met and the initial sparks between them. For example, Minato saving Kushina from a dangerous situation which led to their deep connection.
The main characters are Minato Namikaze and Kushina Uzumaki. Minato is known for his incredible speed and his status as the Fourth Hokage. Kushina, on the other hand, was a strong - willed kunoichi from the Uzumaki clan with powerful chakra.
On a more personal level, they could face internal guilt. As Naruto grows up and achieves great things on his own despite their neglect, Minato and Kushina may realize what they've missed out on. This realization could cause them a great deal of internal turmoil and regret for not being there for their son when he needed them.
A common theme could be the exploration of their relationships. For example, how Minato balances his love for Kushina and his role as a father to Naruko. There could also be a theme of legacy. Minato is a great Hokage, and Naruko could be on a path to follow in his footsteps while being influenced by Kushina's strength. Also, friendship could be a theme, as they support each other through tough times in the village.
It might be due to jealousy. If Minato was getting more attention or praise in the village for his achievements while Kushina felt overlooked, that could create resentment. Say, Minato was constantly being hailed as a hero for his speed and battle tactics, and Kushina, who also had great power, felt like she was in his shadow.
I'm not sure specifically as I haven't read that particular fanfiction. But generally, it might be about Kushina leaving Minato and could explore their relationship, the reasons behind such an action, and how it impacts the Naruto universe within the creative context of the fanfic.
One interesting storyline could be Minato and Kushina's first meeting. Maybe it was a chance encounter in the Hidden Leaf village. Minato, with his natural charm, caught Kushina's attention right away. Another could be their training together, where they learn new jutsu and grow closer as they support each other through tough training sessions.
Maybe a story where they both find themselves in a dangerous situation outside of their respective villages. They have to rely on each other's skills and powers to survive, and in the process, a deep friendship or more could develop. For example, they could be trapped in a mysterious and dangerous forest filled with powerful beasts.
One possible storyline could be that Naruto grows up with a strong sense of family. He would be trained by Minato from a young age, learning advanced jutsu much earlier. With Kushina's loving care, he might not have the same insecurities. For example, he could be more confident in school and among his peers. He might also have a closer relationship with the Uzumaki clan, as Kushina would surely teach him about their heritage.
I'm not sure if there is such a fanfiction specifically. Fanfiction websites have a vast range of works, but 'lemon' fanfictions often contain inappropriate content. It's better to focus on non - explicit fanfictions that explore the relationships and stories in a more positive and appropriate way.
Perhaps in this fanfiction, Naruto turns to the darker side of the ninja world. Since he lacks the love and guidance from Minato and Kushina, he might be more easily influenced by Orochimaru or other villains. He could start to believe that power is the only way to get respect and recognition, and thus embark on a path that is different from his canon self. He might also form unexpected alliances with characters who are also outcasts in the shinobi society.